Sumner-Kalkun, Jason

Psyllids are major vectors of plant diseases, including Candidatus Liberibacter solanacearum (CLso), the bacterial agent associated with 'zebra chip' disease in potatoes and 'carrot yellows' disease in carrot. Despite their agricultural significance, there is limited knowledge on the genome structure and genetic diversity of psyllids. In this study, we provide chromosome-level genome assemblies for three psyllid species known to transmit CLso: Dyspersa apicalis (carrot psyllid), Dyspersa pallida, and Trioza urticae (nettle psyllid). As D. apicalis is recognised as the primary vector of CLso by carrot growers in Northern Europe, we also resequenced populations of this species from Finland, Norway, and Austria. Genome assemblies were constructed using PacBio HiFi and Hi-C sequencing data, yielding genome sizes of: 594.01 Mbp for D. apicalis; 587.80 Mbp for D. pallida; and 655.58 Mbp for T. urticae. Over 90% of sequences anchored into 13 pseudo-chromosomes per species. The assemblies for D. apicalis and D. pallida exhibited high completeness, capturing over 92% of conserved Hemiptera single-copy orthologues, as assessed by Benchmarking Universal Single-Copy Orthologues (BUSCO) analysis. Furthermore, we identified sequences of the primary psyllid symbiont, Candidatus Carsonella ruddii, in all three species. Comparative genomic analyses demonstrated synteny with other psyllid species. Notably, we observed significant expansions in gene families, particularly those linked to potential insecticide detoxification, within the Dyspersa lineage. Resequencing efforts also revealed the existence of multiple subpopulations of D. apicalis across Europe. These high-quality genome resources will support future research on genome evolution, insect-plant-pest interactions, and strategies for disease management.

‘Candidatus Liberibacter solanacearum’ is an economically important pathogen in the Americas, New Zealand and Europe. The primary objective of this review is to systematically investigate the polymerase chain reaction (PCR)-based methods used for its detection in plant samples. Several databases were searched from the inception of the relevant literature up to August 2018. This review identified 53 studies that met all the inclusion criteria. The performance of the different methods was also compared, however due to data heterogeneity and insufficient evidence on the sensitivity of all assays used, a meta-analysis of the data was not possible. Nonetheless, the review indicates that the rtPCR designed to the 16S ribosomal RNA gene can be routinely employed as a fast, cost-effective, and reliable detection technique in diagnostic laboratories.